Process and apparatus for the continuous manufacture of a conveyor belt

ABSTRACT

In a process for the continuous manufacture of a conveyor belt with rubber covering layers and with a reinforcing insert of longitudinal wire ropes, the wire ropes are maintained in tension and covered with an upper and lower covering layer of rubber. The raw belt constructed in this manner is then vulcanized by means of exposure to pressure and heat in a rotating installation. The innermost rubber cover layer in the radial direction is scorched prior to its placement on the outer cover layer and the longitudinal steel wires. 
     An apparatus for the continuous manufacture of a conveyor belt with cover layers of rubber and with a reinforcing insert of longitudinal steel ropes has an extruder-calender arrangement (2, 4 and 3, 5, respectively) each for the production of the lower and upper cover layer (11, 12). At least one doubling installation (15, 17; 22, 23) is provided for the combining of the cover layers (11, 12). Between the extruder-calender (2, 4) producing the cover layer (11) resting on the press drum (16) during the finish vulcanizing process, and the doubling station (22, 23), a heating device (24, 26) is provided for the heating of the cover layer (11).

TECHNICAL FIELD

The invention concerns the continuous manufacture of cable reinforcedconveyor belts. In the process, rubber covering layers are placed onto aband of cables and exposed to a pressing and vulcanizing process.

STATE OF THE ART

Cable-reinforced conveyor belts are usually manufactured in two processsteps. First, the raw belts are fabricated by covering the highlystressed cables with cover layers. The raw belts prepared in this mannerare wound onto a storage roll. For the purpose of vulcanizing theconveyor belts, the raw belts are pressed and vulcanized in a secondprocess step, either in a plate press in sections or continuously in arotating installation. Vulcanizing in a rotating installation has theadvantage of a fully continuous mode of operation (see the journalGummi, Asbest, Kunststoffe 5/1978, pages 328 to 336).

Recently, specialists, in the art have been making attempts to developadvanced production facilities, wherein conveyor belts might befabricated and vulcanized in a single cycle without the intermediatestorage of raw belts. Installations of this type always operate with aplaten press as the vulcanising press because rotating devices are notapplicable for the reason that the steel wires under stress are pullinginto the cover layer that is innermost in the radial direction, againstthe central drum of the press. The accurate center position of thereinforcing insert thus cannot be insured. This is also true for afurther installation for the continuous manufacture of conveyor beltswherein initially in a large extruder a rubber hose with the wallthickness of the conveyor belt and a circumference corresponding to thewidth of the conveyor belt is produced, while the cables are beingembedded simultaneously around the hose. Subsequently, the hose is cutbetween two cables, flattened out and fed continously, withoutinterruption into a rotating installation (DE-OS No. 21 29 439). Hereagain, the steel wires, which are necessarily under stress, are pullinginto the cover layer inside in the radial direction, by virtue of theresultant force.

It has therefore been proposed (DE-AS No. 19 31 972), to compensate thisevasion of the steel wires by means of a suitable design of the coverlayers. The cover layer that is innermost in the radial direction is tobe made thicker than the outercover layer in the radial direction, sothat the steel wires will be in an approximately correct position withrespect to the surface of the conveyor belt. However, this proposal doesnot yield an accurate, defined position of the steel wires in thefinished conveyor belt. Furthermore, the differential structure of theconveyor belt may be a disadvantage under the high operating stresses.

OBJECT

It is the object of the invention to provide a process for theuninterrupted fabrication and vulcanization of conveyor belts reinforcedwith steel wire, wherein a rotating vulcanizing press is used withoutthe above-described disadvantages regarding the position of the steelwires.

DISCLOSURE OF THE INVENTION

The object is attained according to the invention in that the coverlayer innermost in the radial direction is scorched prior to the placingthereon of the outer covering layer and the steel wires, and in that theraw belt is pressed and vulcanized after it has been placed in therotating installation.

The cover layer placed on the center press drum of the rotatinginstallation of the raw belt thus offers higher resistance to the steelwires under stress. Depending on the degree of scorching and theproperties of the rubber mixture, the steel wires may remain in adefined position with respect to the surfaces of the belt.

The invention makes it possible to use rotating presses as thevulcanizing presses in an installation for the uninterrupted fabricationand vulcanizing of conveyor belts.

The invention also concerns an apparatus for the continuous manufactureof a conveyor belt with a continuous rotating installation. Theapparatus is characterized by that an extruding-calendering arrangementis provided for both the production of the lower and the upper coverlayer, that at least one doubler device is present for the combinationof the cover layers and the layer of steel wire, and that a heatingdevice to heat the cover is provided between the extruder-calenderproducing the cover layer resting on the press drum during the scorchingprocess and the doubling station.

Further advantageous embodiments of the apparatus with a continuousrotating installation for the vulcanizing of the built-up raw belt willbe apparent as the following description proceeds in particularreference to the application drawing.

DESCRIPTION OF THE FIGURE

The FIGURE of the drawing comprises a single partially diagramatic sideelevational view of the apparatus according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The apparatus for the uninterrupted and continuous manufacture of aconveyor belt 1 reinforced with steel wire has two extruders 2 and 3,both equipped with wide slit nozzles 4, 5. The wide slit nozzles 4 and 5are followed by two-roll calenders 6, 7. Each two-roll calender 6 and 7,respectively, is followed in turn by a conveying roll segment 8, 9 forthe rubber sheets leaving the two-roll calenders 6, 7. The lower rubbercover layer 12 is placed by a pressure roll 13 under slight pressureonto an endless steel back pressure belt 14, which at this point hasjust been guided back by means of a tail sheave 15 to a central pressuredrum 16. Between the tail sheave 15 and the press drum 16 the endlesssteel back pressure belt 14 forms a horizontal bearing surface.

The tail sheave 15 is associated with a pressure loaded double roll 17upon which a set of parallel steel wires 18, coming from a grooved roll19, is running. The steel wires 18, coming from a spool rack (notshown), are stressed by a roll tensioning device 21. Between the firstdoubling station 15, 17 and the press drum 16 is arranged a seconddoubling station comprising two rolls 22 and 23. The second, upperrubber cover layer 11 runs onto the circumference of the upper, pressureloaded doubling roll 23. The cover layer 11, produced by the upperextruder-calender 2, 4 is guided over a heating drum 24, after passingover a pressure roll 25. The angle of contact in the embodimentillustrated is approximately 200°. After leaving the heating drum 24,the cover layer 11 is further heated by a radiating heater body 26. Itmay be appropriate in the case of rubber mixtures tending to be porousto provide the heater drum 24 with a pressure hoop partially surroundingsaid heater drum 24.

The central pressure drum 16 is partially surrounded by the endlesssteel belt 14 guided by the tail sheaves 27, 28, 29 and 15, whileforming a pressure segment. The reverse side of the endless steel belt14 is heated by a curved radiation heating device 31 in the area whereinit surrounds the pressure drum 16.

BEST MODE OF THE EMBODIMENT OF THE INVENTION

The two rubber cover layers 11, 12 are produced by the extruder-calender2, 4 and 3,5. The lower cover layer 12 is placed by way of the conveyingroll segment 9 and by means of the pressure roll 13 onto the endlesssteel belt 14 and guided to the first doubling station 15, 17, wheresteel wires 18, tensioned and held parallel by means of the guide pulley19, are pressed into the lower cover layer 12. The cover layer 12 withthe impressed steel wires 18, is moved to the second doubling station22, 23 on the endless steel belt 14. In this second doubling station 23,23 the upper cover layer is applied. The upper cover layer 11 is guidedprior to this over the circumference of the heating drum 24 and past theradiating heater body 26. The surface of the cover layer 11 facing theheating drum 24 and the radiating heater body 26 is exposed tocontrolled scorching by means of this heating. The raw belt 32constructed in this manner is directed into the rotating press formed bythe drum 16 and endless belt 14. In the compression segment formed bythe portion of the endless steel belt 14 surrounding the drum 16, theraw belt 32 is compressed and vulcanized. Heat is supplied by means ofheating the press drum 16, with the reverse side of the belt beingheated by means of the curved radiating heater body 31 positioned on thereturn side of the steel belt 14. After leaving the compression segment,the vulcanized conveyor belt 1 is separated from the return leg of theendless steel belt 14 and transported to further processinginstallations.

The steel wires 18, stressed in tension, cannot pull into cover layer11, that is, the inner layer when viewed in the radial direction in thecourse of their passing through the compression segment, by virtue ofthe scorched and thus harder surface of the upper cover layer 11. Theshifting of the steel wires 18 is no longer possible. With knowledge ofthe mixture of rubber used, the position of the steel wires 18 in theconveyor belt 1 can be determined with accuracy. The controlledscorching of the cover layer 11 enables this layer to offer apredetermined resistance to the penetration of steel wires 18, dependingon the mixture of rubber and the degree of scorching, during theirpassage through the compression path around the press drum 16.

It is possible within the scope of the process described hereinabove torun adhesion promoting layers between the cover layers. Such adhesionpromoting layers are known in themselves. It is also possible to embedthe layer of steel wires in a thin, adhesive layer of rubber prior tothe first doubling station.

INDUSTRIAL APPLICABILITY

By means of the process and apparatus according to the invention, cablereinforced conveyor belts may be produced continuously. For the firsttime, it is possible to insure the accurate central position of theparallel cable reinforcements in continuous production. Conveyor beltsmade by the process of the invention or on an apparatus according to theinvention are capable of long life and operating safety in spite ofextreme stresses in use. The production of cable reinforced conveyorbelts of high quality is thus more economical.

I claim:
 1. A process for the continuous manufacture of conveyor beltswith covering layers of rubber and a reinforcing insert of longitudinalwire ropes, comprising the steps of:(a) tensioning and holding parallelsaid wire ropes; (b) pressing in a first station said tensioned wireropes into a lower cover layer; (c) applying in a second station spacedfrom said first station an upper cover layer over said wire ropes, saidupper cover layer, prior to said second station, passing through heatingmeans to effect controlled scorching and thus surface hardening of saidupper cover layer, and thereafter, in a continuous manner; (d) passingsaid raw belt comprising said cover layers and said wire ropes through acompressing and vulcanizing zone to form the completed belt, with saidupper cover layer being the radially inner layer when passing throughsaid zone.
 2. The process of claim 1 wherein said controlled scorchingof said upper cover layer is effected by first passing said upper layerover a substantial portion of the circumference of a rotating heatingdrum and thereafter passing said layer contiguous to an elongatedradiating heater.
 3. The process of claim 1 wherein said step ofcompressing and vulcanizing is effected by passing said raw belt betweena rotating heating drum and an endless belt, the radially outer side ofsaid raw belt being heated by a curved radiating heater disposedradially outwardly adjacent said endless belt and traversing asubstantial portion of the circumference of said heating drum. 4.Apparatus for the continuous manufacture of conveyor belts havingcovering layers of rubber with a reinforcement insert of longitudinalwire ropes, comprising:(a) means for extruding separately first andsecond cover layers; (b) means for tensioning and holding parallel saidwire ropes; (c) a first station at which said tensioned wire ropes arepressed into said first cover layer; (d) means for heating and effectingcontrolled scorching and thus hardening of said second layer; (e) asecond station spaced from said first station for applying said secondcover layer to said wire ropes and said first cover layer to form a rawbelt, and (f) vulcanizing means through which said raw belt passes forcompressing and vulcanizing said belt, said scorched second layer beingthe radially inner layer when said belt passes through said vulcanizingmeans.
 5. The apparatus of claim 4 further including anextruder-calender for simultaneously forming each of said first andsecond cover layers, and a first doubling station comprising a rollsuperimposed over a sheave and between which said first cover layer andsaid wire ropes pass and are compressed.
 6. The apparatus of claim 5further including a second doubling station positioned between saidvulcanizing means and said first doubling station, said second doublingstation comprising first and second superimposed rolls between whichpass said first and second cover layers and said wire ropes positionedtherebetween, said raw belt being formed at said second doublingstation.
 7. The apparatus of claim 5 wherein said vulcanizing meanscomprise a rotatable heating drum and a rotating endless belt, with saidraw belt being carried and compressed between said endless belt and saidheating drum, and further comprising a curved radiating heater disposedradially outwardly of and contiguous to said endless belt.
 8. Theapparatus of claim 4 wherein said means for heating and effectingcontrolled scorching of said second cover layer comprises a secondrotating drum around which said second cover layer passes, and anelongated radiating heater along which said second cover layer passes.9. The apparatus of claim 5 wherein said sheave is positioned relativeto rotatable heating drum so that an endless belt positioned over saidsheave and passing around a portion of said drum has a horizontalbearing surface at the inlet side of said drum.